The successful Miller theory of "carcinogen as electrophile" has focused much attention on the reactivity of chemical carcinogens as carbonium ions or nitrenium ions. However, many carcinogens also display free radical chemistry and, in fact, the major site of attack of carcinogenic aromatic amines is C-8 of guanine - the site of attack of free radicals. The objective of this project is to provide an up to date understanding of the free radical and associated ionic reactivity of two chemical classes of mutagens and carcinogens so as to provide a sounder basis for evaluating the reactions of these substances in vitro and in vivo. In particular, we will study chemical conditions (thermolysis, molecule induced homolysis, one electron transfer) which lead to homolytic rupture as it competes with heterolytic rupture of the O-O bond of diacyl peroxides and the N-O bond of N-acyloxy-arylamines, N-acyloxyarylacetamides and 1,N-diacyloxy-quinolin-4-amine. We will employ the cyclobutyl group as a structural probe of ionic reactions, and 13C-CIDNP as a probe of radical pair reactions. Radical/ion reactivity profiles will be established with the aim of seeking a correlation between the reactivity profile and compound mutagenicity proffle in Salmonella and B. subtilis bacterial tester strains.